Sludge phase reactor and process for performing sludge phase reactions

ABSTRACT

A reactor is described for exothermic sludge phase reactions which comprises as the heat exchanger an annular chamber which is covered at the top and the bottom by the reaction mass in the reactor, the annular chamber comprising a plurality of vertical passage ducts having a circular cross-section for the reaction mass, and the coolant flowing through the annular chamber between the passage ducts for the reaction mass.

This continuation-in-part application, which is designated for filing inthe United States, corresponds to PCT Application number PCT/EP95/03786, which was filed on Sep. 25, 1995 and claims priority over DEApplication No. P 44 35 839.3, which was filed on Oct. 7, 1994.

BACKGROUND OF THE INVENTION

Sludge phase reactions are reactions in which at least one finelydivided solid phase and one fluid phase participate.

Highly exothermic sludge phase reactions require effective discharge ofthe heat of reaction. Sludge phase reactors therefore thus generallyinclude expensive heat exchanger constructions inside the reactioncontainer (see, e.g., U.S. Pat. No. 3,243,268 or European patent263,935). In the case of the known sludge phase reactors, the heatexchange is brought about as a result of the fact that the reaction massis pumped around so-called "field" heat exchanger pipes or boiler pipeswhich are closed at one end and in which the heat-transfer medium andthe resultant steam are guided counter-currently. The disadvantage ofthis type of heat exchange is the flow speed of the reaction mass whichdiffers in relation to the reactor chamber and the low degree ofefficiency of the heat exchanger brought about thereby. The differentflow speed of the reaction mass gives rise to areas in which the flow issubstantially decreased and the solid components involved in thereaction can be deposited.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-section through the sludge phase reactor accordingto the invention; and

FIG. 2 shows is a cross-sectional view of the reactor of FIG. 1 in thedirection of A--A of FIG. 1.

DESCRIPTION OF THE INVENTION

In accordance with the invention it is now proposed to provide as a heatexchanger a container through which the heat-transfer medium essentiallyflows in one direction only, the container being equipped with aplurality of passage ducts having a circular cross-section for thereaction mass. In accordance with the invention the reaction mass isconsequently guided "inversely" in the heat exchanger in comparison withconventional evaporation- heat exchangers.

The subject matter of the present invention is a sludge phase reactorfor exothermic sludge phase reactions, comprising the followingcomponents:

a) a reaction container;

b) a heat exchanger in the form of an annular chamber through which thecoolant and the reaction mass flow inside the reaction container, theannular chamber being covered at the top and bottom by the reactionmass;

c) a central free flow chamber inside the annular chamber for the returnflow of the reaction mass;

d) a central agitator which circulates the reaction mass between thecentral free flow chamber and the annular chamber;

wherein the annular chamber comprises a plurality of vertical passageducts having a circular cross-section for the reaction mass, and thecoolant flows through the annular chamber between the passage ducts forthe reaction mass.

Preferably reaction mass and heat-transfer medium flow through the heatexchanger annular chamber substantially in the same direction. Inparticular the passage ducts for the reaction mass through the annularchamber are flowed through vertically upwards. In this case the agitatoris preferably disposed at the lower outlet of the central free flowchamber. At least one of the reaction components is delivered in theimmediate vicinity of the agitator such that firstly the reactioncomponent is rapidly distributed in the reaction mass and secondly thedelivered reaction component with the reaction mass is introduced veryrapidly into the heat exchanger.

In order for the reaction to be performed continuously, an overflow fromwhich reacted reaction mass can be continuously drawn off is providedabove the fluid level in the reaction container.

Preferably a substance which evaporates at the reaction temperature andwhich is delivered in liquid form at the base of the heat exchangerannular chamber and is drawn off in gaseous form from the head of theheat exchanger annular chamber is used as the heat-transfer medium.Particularly preferably, water is used as the heat-transfer medium andthe heat exchange takes place with the production of steam. The coolanttemperature is preferably set by maintaining the pressure of the steamproduced.

Preferably reactions involving a gas phase are performed in the sludgephase reactor according to the invention. To this end the agitator is inthe form of a gassing agitator or comprises an additional gassingcomponent.

The sludge phase reactor according to the invention and having a gassingagitator is particularly suitable for performing the sludge phasehydrogenation of aromatic nitro compounds, particularly preferably forthe hydrogenation of dinitrotoluenes with the production of thecorresponding diamines.

The invention will be explained in greater detail with reference to theattached drawings.

The reactor according to FIG. 1 comprises a reaction container 1 whichis constructed from three parts which are flanged together by means offlanges 11 and 12. The central part of the reaction container 1 containsthe annular heat exchanger 2 which comprises an annular chamber closedon all sides and is penetrated by a plurality of passage pipes 21through which the reaction mass flows rising in the direction indicatedby the arrows. Located in the remaining space 22 of the annular chamber2 is the heat-exchanger medium. As indicated by arrows, the return flowof the reaction mass is through the central free flow chamber 3 insidethe annular heat exchanger 2. The circulating flow of the reaction massis brought about by the agitator 4 with a central agitator shaft 41,driven externally of the reactor, and an agitator blade 42. In thisrespect the agitator blade 42 is disposed at the bottom, at the level ofthe outlet from the central flow chamber 3. In the embodimentillustrated the agitator shaft 41 is in the form of a hollow shaft andcomprises a gassing device 43 below the agitator blade 42. The gas forgassing the reaction mass is drawn out of the gas chamber in the upperpart of the reaction container 1 by means of intake openings 44 in theagitator shaft 41. A predetermined gas pressure is ensured via the gasdelivery connection 45. When the reactor according to the invention isused as preferred for hydrogenating aromatic nitro compounds, hydrogenis used at a pressure of between 10 and 40 bar. More advantageously,fresh hydrogen can be delivered directly into the reaction mass. Thearomatic nitro compound is introduced via delivery line 5 into theimmediate vicinity of the agitator blade 42. Precious metals or nickelfor example on carrier particles such as carbon, SiO₂, Al₂ O₃ and thelike or Raney-nickel catalysts are dispersed in the reaction mass as thefinely divided solid phase. The product is continuously drawn off at theoverflow 7 so that a constant fluid level is maintained. The heatexchanger annular chamber is further supplied from a heat exchangermedium circuit 6. The heat exchanger medium, preferably water just belowboiling point, is introduced into the bottom of the heat exchanger at61. Steam emerges from the top of the heat exchanger at 62 and isdelivered to the steam separator 63. The arrow 64 indicates thedischarge of the steam for the recovery of energy. The cooling waterinflow valve 65 is controlled by means of a level regulating device 66for the water level in the steam separator 63. When the reactoraccording to the invention is used as preferred for hydrogenatingaromatic nitro compounds, the coolant pressure 64 is regulated so that atemperature of 120° to 250° C. is maintained in the reactor.

The numerals in FIG. 2 designate the same components as in FIG. 1. Onlysome of the passage pipes 21 are shown. The heat exchanger 2 cancomprise between 100 and 3000 passage pipes 21 depending on the nominalwidth of the pipes (25-10 mm) and the diameter of the heat exchanger (upto 3 m).

Although the invention has been described in detail in the foregoing forthe purpose of illustration, it is to be understood that such detail issolely for that purpose and that variations can be made therein by thoseskilled in the art without departing from the spirit and scope of theinvention except as it may be limited by the claims.

What is claimed is:
 1. A sludge phase reactor for exothermic sludgephase reactions comprising:(a) a reaction container; (b) a heatexchanger disposed within said reaction container, said heat exchangerin the form of an annular chamber through which heat-exchanging mediumand reaction mass flow; (c) wherein said annular chamber comprises aplurality of open-ended vertical passage ducts having a circularcross-section for said reaction mass, and wherein said heat-exchangingmedium flows through said annular chamber between said passage ducts forsaid reaction mass; (d) a central free flow chamber inside the annularchamber for the return flow of the reaction mass; (e) a central agitatorwhich circulates the reaction mass between the central free flow chamberand the annular chamber; (f) wherein said agitator is additionally inthe form of a gassing agitator; and (g) wherein said agitator conveyssaid reaction mass downwards in said central flow chamber and producesan upward flow in said vertical passage ducts.
 2. The sludge phasereactor of claim 1, wherein the agitator is disposed at the outlet ofthe central free flow chamber and is formed with accessible walls. 3.The sludge phase reactor of claim 1, wherein at least one reacting agentis introduced into the reaction mass in the immediate vicinity of theagitator.
 4. A sludge phase reactor according to claim 1, wherein saidheat exchanging medium and said reaction mass flow through said annularchamber in substantially the same direction.